Facebook today is taking another step ahead in its ad targeting strategy, which serves users advertising based on their location and online purchasing and browsing histories. The social network is launching partner categories: some 500 “unique groups”, with more to come, which are descriptors (one example: “buyers of children’s cereals”) that match up with relevant people among Facebook’s 1 billion+ users. Facebook says that advertisers can “futher refine” the categories by using other targeting options it already offers.

As with Facebook’s other targeting ad-tech news, Datalogix, Epsilon and Acxiom will be among the companies providing data to power the service. Datalogix alone says it will be providing some 300 of these audience segments.

This is one of the first official products to come out of the partnership with these ad targeting data specialists, which were first tested in September 2012 and then officially announced in February. (Two other stories looking at how these partnerships are progressing are here and here.)

While Facebook has been rolling out some features in ads and in its user services by platform — for example, mobile-only and desktop-only — it’s perhaps a measure of how important this is to the company that it is being rolled out across both desktop and mobile ads today.

Targeting using data from the wider web is a big progression on Facebook’s existing advertising services. Facebook, of course, has been relying on user information to target ads on its site before this, but only relying data that has been picked up within Facebook itself (although that’s an area that is also expanding). Ad targeting techniques like the ones being introduced today are used on the wider web, so it is important for Facebook to have them as well if it wants to continue to pick up ever-larger parts of businesses’ online marketing budgets.

Facebook’s had one crucial client win this week in that vein: General Motors is back to testing out ads for Facebook after pulling its marketing there a year ago. Its recent acquisition of Atlas from Microsoft also fits into this bigger strategy of having an all-in-one platform for providing online advertising services to businesses.

As you can see from the screenshot of how it looks below, Partner Categories provides a number of relevant details for each category — but not any information about specific users. They include how many people are in a category — 14.8 million for kids’ cereal! — and some of the purchasing history that goes into them getting put into that group. That includes how often a product is bought over the last year, and details of where the information got sourced.

For users, there are the inevitable pros and cons. On the one hand, you will be seeing ads that, in theory, will be based on things you are interested in (if you could call Cap’n Crunch an interest, that is).

“Our ultimate goal is to make the ads people see on Facebook as relevant as the information they see from their friends,” Yvette Lui, director of global marketing solutions, global data & audience partnerships at Facebook, noted in a news release put out by Epsilon. “Targeting features like custom audiences and partner categories help make this possible. Our partnership with Epsilon gives marketers a more accurate and effective way to reach the right groups of real people, which makes for a better ad experience.”

But… on the other, it’s always slightly annoying and menacing when you’ve browsed online for, say, plane tickets to Guatemala — and perhaps even purchased them already — and yet continue to get served ads for related plane tickets everywhere else you visit on the web.

Indeed, while this gives advertisers a lot more detail about how, where and to whom to serve ads, what it does not do is ensure that those advertisers will necessarily be the most relevant matches for you. For example, it’s not a guarantee that the kids’ cereal buyer category will only be used by Kellogg’s or Quaker Oats. It might be a vitamin or toy company, or any kids product company, or any company selling things to parents, or really any company at all that may decide to serve an advert to that particular product category.

As with other targeting services on Facebook, a user can opt out of getting ads from specific advertisers, or from targeting altogether.